Michael May lost his sight at age 3 in an accident and over 40 years later stem cell therapy helped restore sight to one eye. A few years later it is clear that parts of his brain that do image processing never developed and show no signs of going thru the necessary development now.
He can discern motion, two-dimensional forms and color. "That was the most amazing thing. Initially I hadn't thought about color. To all of a sudden have the faucet turned on for this whole world of colors, it was amazing. Somewhere in the recesses of my mind was the ability to discern colors," May said in a telephone interview.
What he can't do is recognize objects in three dimensions, make sense of complex landscapes, recognize faces or interpret facial expressions.
Fine and Donald MacLeod of the University of California at San Diego have conducted a battery of tests. Brain scans showed that the part of the brain that becomes activated in sighted people when they see faces and objects remained dormant in May. But when he looks at an object that is moving, the motion detection part of his brain lights up with activity.
The findings suggest that certain visual skills, such as detecting color and motion, are more hard-wired and develop earlier in infancy than others.
When asked to identify a cube illustrated on a two-dimensional computer screen, for example, Mr. May failed. But once Miss Fine commanded the cube to rotate, simulating motion in three dimensions, he immediately recognized it.
One scientist likens it to how it is easier to learn languages when younger than when older. This result is also consistent with experiments done on cats decades ago where their heads were kept in harnesses when they were young and they were only shown vertical or horizontal lines for a key number of weeks (its been too long since I learned this to recall it with precise detail). After that the cats which had been exposed to vertical bars could recognise them but not recognise horizontal bars. The cats exposed to horizontal bars during the critical developmental period could see only horizontal bars.
It may eventually become possible to feed neural stem cells and hormones to the part of the mind that processes sight in order to get it to revert to a more plastic state so that in cases where sight is restored the mind can once again go thru the process of learning how to see.
|Share |||Randall Parker, 2003 August 24 11:59 PM Biological Mind|